Neuropathic pain can be caused by various diseases, such as viral infections and diabetes. For example, post herpetic neuralgia is caused by herpes viral infection and cause moderate to severe pain in the infected skin area to the subject. Various drugs and formulations have been used to treat neuropathic pain with varying degrees of success. There is an ongoing need to treat this type of pain, accordingly, research continues into methods of treating neuropathic pain in a manner that is rapid-acting and long lasting.